An Agonalia was an obscure archaic religious observance celebrated in ancient Rome several times a year, in honor of various divinities. Its institution, like that of other religious rites and ceremonies, was attributed to Numa Pompilius, the semi-legendary second king of Rome. Ancient calendars indicate that it was celebrated regularly on January 9, May 21, and December 11.
Some thought the Romans had a god named not by chance “Agonius”, who might then have been the god of the Colline part of the city.
January 9 was the Agonalia or Festival to Janus, god of gates and doorways.
There really a veriety of egends about the history of Janus. One has him the son of Uranus and Hecate, while another says he had a son named Tiberinus whose accidental drowning named Roma’s river. According to another legend, he was a son of Apollo and the first king of Latium. His colony near the Tiber is supposed to have given the name to the Janiculum Hill. Another story says that Janus welcomed Saturn to earth after the latter was driven out of Olympia by Zeus.
Not much is known about how this festival was celebrated. Apparently, during this festival, the Romans gave dates, figs, and honey sealed in white jars to the god Janus. Such gifts, and also money, would be given to family members as well.
This was a festival originally for the protection of the king, and a ram was the usual sacrifice victim, probably originally held on the Quirinal Hill.
The Romans said that today Janus flew over the doors and gates, which were cleaned to perfection, in his honor.
In any case, Janus was very important in Rome because the weakest point in any building or municipality is, not by chance, its doorway and anything from human enemies to evil spirits could enter via that route. So strong was this feeling that Romans always carried corpses out of buildings feet first so that the departed spirits would be less likely to find their way back in.
In 260 BC the Romans built an important gateway temple to Janus after a victory against the (previously) unbeatable Carthaginian fleet. This was left open in times of war and closed when the armies had returned to the city.
On current days this seems a little bit strange, but not for Romans: during the time the gateway was open, Janus was out fighting for Rome while when it was closed it meant that the god would not abandon the city!